The breadth of medical knowledge has grown to a level that even health professionals can hardly remember and use all information relevant to their specialty. In addition, this information is growing so quickly that any individual will have difficulty staying up to date. For example, health issues are addressed in ever-increasing tens of thousands of online sites, with potentially millions of pages of health related information. Also, a significant portion of medical information is stored in many searchable databases available to health professionals.
A different type of medical information exists in the clinical data collected as personal health records of individuals. Each personal record may include multiple items of different types including conditions, symptoms, diagnoses, test results, medications, allergies, and procedures. These items may have been reported by the individuals themselves, based on their medical claims, or collected by health professionals, such as physicians, or nurses, in the physician's offices or in hospitals. The patients and the health professionals need to utilize the generally available medical knowledge, such as relationships among these items, in order to monitor and manage a patient's diagnosis over time.